Dot notation extension for SassyMap's map-get-deep Sass function

_map-get-deep-dot.scss

/**
 * Fetch a deeply nested value in a multi-level map using object dot-notation string OR a list of keys.
 *
 * @requires sassy-maps
 * @requires SassyLists
 * @requires is-map
 * @requires is-string
 * @requires is-list
 *
 * @param {map}           $map
 * @param {string | list} $keys         object dot-notation string representing the nesting order of the desired key
 * @param {string}        $delimiter    string used to identify the individual keys within the string
 *
 * @throws if any of the `$required-functions` do not exist
 * @throws if `$map` param is not a map
 * @throws if `$keys` param is not a string or a list
 *
 * @return {*} value at nesting level requested via `$keys` param
 */
@function get($map, $keys, $delimiter: '.') {
    $required-functions: is-map, is-string, is-list, sl-explode, map-get-deep;
    @each $function in $required-functions {
        @if not function-exists($function) {
            @warn "`#{$function}()` is required by `get()`.";
            @return null;
        }
    }
    @if not is-map($map) {
        @warn "`get` function expecting a map; #{type-of($map)} given.";
        @return null;
    }
    @if not is-string($keys) and not is-list($keys) {
        @warn "`get` function expecting a list or a string; #{type-of($keys)} given.";
        @return null;
    }
    // END error-checking

    @if is-list($keys) {
        //
        // its already a list, no need to split it
        //
        @return map-get-deep($map, $keys);
    } @else {
        @if not str-index($keys, $delimiter) {
            //
            // a single key has been requested - no recursion necessary
            // (no `$delimiter` found in `$keys`)
            //
            @return map-get($map, $keys);
        } @else {
            //
            // a `$delimiter` was found in the `$keys` string
            // lets split it on the delimiter so we can pass a valid list of keys to `map-get-deep()`
            //
            $key-list: sl-explode($keys, $delimiter);

            @return map-get-deep($map, $key-list)
        }
    }
}

Since you are using SassyLists anyway, you could use the every function to do your initial check.

@if not every($required-functions, function-exists) {
  @warn "Missing dependencies.";
  @return null;
}